Olefin oligomerization using boron trifluoride and a three-component cocatalyst

ABSTRACT

Olefin oligomers suitable as lubricants are prepared with a catalyst comprising boron trifluoride and a mixture of an alcohol, a polyol and a ketone. 1-Decene is oligomerized to a liquid product having a high trimer to tetramer ratio using boron trifluoride and a mixture of n-butanol, ethylene glycol and methylethyl ketone.

SUMMARY OF THE INVENTION

Olefins are oligomerized using a four-component catalyst combinationcomprising boron trifluoride and a mixture of an alcohol, a polyol and aketone. When 1-decene is oligomerized using boron trifluoride and aliquid mixture of n-butanol, ethylene glycol and methylethyl ketone, theresulting liquid oligomer is produced in good yield with a high trimerto tetramer ratio.

DESCRIPTION OF THE INVENTION

Oligomers of certain 1-olefins are highly useful in preparing functionalfluids such as lubricants, hydraulic fluids, transmission fluids,transformer fluids, and the like, generally compounded with otherfunctional fluid components including appropriate additives. Eachfunctional fluid product and generally the base fluid from which it isprepared must conform with established viscosity and volatilityspecifications. These alpha-olefin oligomer products are generallyprepared by the cationic polymerization of the 1-olefin using aFriedel-Crafts catalyst, preferably boron trifluoride. The oligomerproduct is then hydrogenated in a conventional manner to stabilize theoligomer against oxidation and degradation.

In recent years 1-decene oligomer mixtures have been widely used inengine lubricant and hydraulic fluid formulations. Using conventionalreaction conditions, the 1-decene polymerization reaction prepares amixture of the oligomers including the dimer, trimer, tetramer, andpentamer comprising branched-chain molecular structures in which thebranches are of relatively long carbon length. The dimer is removed forseparate use to avoid volatilization loss from functional fluidscomprising the higher oligomers. Minor amounts of oligomers higher thanthe pentamer, such as the hexamer, may be present but since theiranalysis and separation from the pentamer is difficult, they, ifpresent, are generally reported as pentamer.

The composition of the oligomer mixture that is obtained from theoligomerization reaction is generally too rich in the tetramer andpentamer fractions to meet the viscosity specifications for desiredformulations. This usually requires the separation of the oligomercomposition into one or more product fractions comprising the trimer ora mixture of oligomers, rich or predominating in the trimer, dependingon the particular need. And most significantly, this generally resultsin a significant unusable surplus of the higher oligomer fractions to bediscarded, namely, the tetramer and pentamer fractions, as reported inU.S. Pat. No. 3,997,627. As a result those working in this field havedirected their efforts towards increasing the selectivity of the1-decene oligomerization reaction to the trimer, often referred to asimproving the trimer to tetramer ratio or the ratio of the trimer to theheavier fractions.

The catalyst generally recommended for the oligomerization of 1-olefinsis boron trifluoride and a liquid cocatalyst. The boron trifluoride mustbe present in molar excess of the cocatalyst for optimum results. Avariety of substances have been used or suggested for use as thecocatalyst including water, various alcohols, ethers, polyols, aliphaticcarboxylic acids, anhydrides, esters, and ketones, all of which arespecified for this use in U.S. Pat. No. 4,045,507.

We have discovered that the combination of boron trifluoride catalysttogether with a mixture of certain cocatalyst substances, and morespecifically a mixture of an alcohol, a polyol and a ketone,beneficially affects the oligomerization reaction and also benefits theresulting oligomer product. For example, when 1-decene is oligomerizedusing boron trifluoride, and this three-component cocatalystcombination, both the conversion and the trimer to tetramer ratio areimproved.

The alcohol which is suitable in our cocatalyst mixture is an aliphaticalcohol having from one to about ten carbon atoms or a mixture thereof,preferably from about two to about four carbon atoms. This alcohol isused in the amount of about 50 to about 98 weight percent, preferablyabout 75 to about 95 percent of the total cocatalyst combination.Suitable alcohols include methanol, ethanol, propanol, isobutanol,n-decanol and the like. The preferred alcohols are the two to fourcarbon alcohols, and the most preferred alcohol is n-butanol.

The polyol which is used in our cocatalyst combination is selected fromethylene glycol, propylene glycol, butane diol, glycerine, and the like.A two or three carbon diol is preferred. The polyol or mixture ofpolyols are present in the amount of about one to about 25 weightpercent, preferably about two to about 15 percent of the totalcocatalyst combination. The ketone which is used is selected fromaliphatic ketones having from three to about ten carbon atoms andmixtures thereof, or preferably ketones having three or four carbonatoms such as acetone, methylethyl ketone, methyl n-butyl ketone, andthe like. The ketone is also present broadly in the range between aboutone and about 25 weight percent, preferably within the range of abouttwo to about 15 percent.

The cocatalyst mixture can be used in a catalytic amount such as fromabout 0.01 to about 3.0 weight percent of the olefin undergoingoligomerization, preferably from about 0.1 to about 1.0 weight percent.

The oligomerization reaction is carried out using the four-componentcatalyst described herein and using conventional reaction conditions andprocedures. Thus, the oligomerization can be carried out as a batchreaction as described in U.S. Pat. No. 3,780,128 or it can be carriedout as a continuous reaction such as described in U.S. Pat. No.4,045,507. Other types of oligomerization reactors and reaction systemsare also suitable for use with our novel catalyst system. In general,any equipment or production layout designed for oligomerization withboron trifluoride catalyst can be used with our catalyst.

The oligomerization reaction is conducted within the temperature rangeof between about -20° C. to about 90° C. with a temperature within therange of between about 20° C. and about 70° C. being preferred. Thepartial pressure of boron trifluoride in the oligomerization reactor isbroadly maintained within the range of between about five and about 500psig or higher, with a range of between about 20 and about 100 psigbeing preferred.

The olefins which can suitably be oligomerized by the novel catalystdescribed herein have between about six and about 20 carbon atoms,preferably between about 10 and about 14 carbon atoms. The olefins canbe straight-chain or branched-chain olefins and can be alpha-olefins orinternal olefins. The preferred olefins are normal alpha-olefins. Whenolefins having more than 13 carbon atoms are oligomerized, the dimer maybe the preferred oligomer fraction.

DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLES 1-5

1-Decene was oligomerized in a series of experiments using borontrifluoride and a cocatalyst mixture comprising n-butanol, methylethylketone and ethylene glycol. These experiments were carried out at steadystate conditions by the continuous process described in U.S. Pat. No.4,045,507 using two stirred tank reactors in series. The operatingconditions and product analyses are set out in Table I.

                  TABLE I                                                         ______________________________________                                        Example     1       2       3      4     5                                    ______________________________________                                        Cocatalyst, wt %                                                              n-butanol   100     91.4    91.4   91.4  80                                   me. eth. ketone                                                                           0       5.8     5.8    5.8   10                                   eth. glycol 0       2.8     2.8    2.8   10                                   Cocat. conc., wt %                                                                        0.56    0.66    0.80   0.36  0.40                                 BF.sub.3, conc., wt %                                                                     0.63    0.79    0.81   0.55  0.65                                 Temperature, °C.                                                                   49-52   49-50   53     51-52 48-51                                Pressure, psi                                                                             20      20      20     31-32 30                                   Product, wt %                                                                 C.sub.10    10.0    7.3     9.3    7.7   5.5                                  C.sub.20    7.8     10.6    11.4   11.9  15.0                                 C.sub.30    50.1    58.3    58.3   55.4  55.5                                 C.sub.40    25.2    19.9    17.8   19.4  20.2                                 C.sub.50    6.9     3.9     3.2    5.6   3.8                                  C.sub.30 /C.sub.40+                                                                       1.56    2.45    2.78   2.22  2.31                                 ______________________________________                                    

It is noted from Table I that both the conversion and the trimer totetramer and higher ratio is improved in all instances where the novelfour-component catalyst combination was used.

The monomer and dimer were removed from each of the products fromExamples 1 and 3. Each of the remainder portions was distilled into atrimer-rich fraction having a 210° F. viscosity of about 4 cSt and atetramer-rich fraction having a 210° F. viscosity of about 6 cSt. Theweight ratio of the 4 cSt fraction to the 6 cSt fraction resulting fromExample 1 was 1.7:1, while the ratio of these fractions resulting fromExample 3 was 3.3:1.

EXAMPLES 6-7

Two more experiments were carried out in the reactor system used in thepreceding examples. 1-Decene was oligomerized using boron trifluoridecatalyst at a concentration of 0.67 wt % and a n-butanol concentrationof 0.58 in Example 6. In Example 7 the catalyst concentration was 0.73weight percent boron trifluoride and 0.64 percent of a cocatalystmixture consisting of about six percent methylethyl ketone, threepercent ethylene glycol and the remainder n-butanol. The temperatures inthe reactors were 41°-45° C. and the pressures were 19-22 psi. Theproducts were separated into 4 cSt and 6 cSt fractions, as described inconnection with Examples 1 and 3. The ratio (weight) of the 4 cStfraction to the 6 cSt fraction produced in Example 6 using puren-butanol as the cocatalyst was 1.3:1, while the ratio resulting fromthe use of the three-component cocatalyst was 3.1:1. The two fractionsobtained using the three-component cocatalyst were analyzed and theviscosities (ASTM-D445 ) and viscosity indexes were determined. Thisinformation is set out in Table II.

                  TABLE II                                                        ______________________________________                                        Fraction          4 cSt    cSt                                                ______________________________________                                        Composition, wt %                                                             C.sub.20          0.5      --                                                 C.sub.30          79.3     26.6                                               C.sub.40          20.2     52.0                                               C.sub.50          --       21.4                                               Viscosity, cSt                                                                at -40° F. 2,465    7,269                                              at 0° F.   334      813                                                at 100° F. 18.42     33.09                                             at 210° F.  3.98     5.95                                              Viscosity Index   125      138                                                ______________________________________                                    

It is to be understood that the above disclosure is by way of specificexample and that numerous modifications and variations are available tothose of ordinary skill in the art without departing from the truespirit and scope of the invention.

We claim:
 1. A process for producing a mixture of olefin oligomers whichcomprises contacting an olefin having from about six to about 20 carbonatoms or a mixture thereof with a catalyst comprising boron trifluorideand a cocatalyst comprising between about 50 and about 98 weight percentof an aliphatic alcohol having from one to about ten carbon atoms,between about one and about 25 percent of an aliphatic ketone havingfrom three to about ten carbon atoms and about one to about 25 percentof a polyol selected from ethylene glycol, propylene glycol, butane dioland glycerine.
 2. A process for producing a mixture of olefin oligomersin accordance with claim 1 wherein the olefin is an alpha-olefin havingbetween about ten and about 14 carbon atoms or a mixture thereof.
 3. Aprocess for producing a mixture of olefin oligomers in accordance withclaim 1 wherein the partial pressure of the boron trifluoride is betweenabout five and about 500 psig, the cocatalyst mixture comprises betweenabout 0.01 and about 3.0 weight percent of said olefin, and thetemperature is between about -20° C. and about 90° C.
 4. A process forproducing a mixture of olefin oligomers in accordance with claim 1wherein the cocatalyst comprises between about 75 and about 95 percentof the aliphatic alcohol, between about two and about 15 percent of thealiphatic ketone and between about two and about 15 percent of thepolyol.
 5. A process for producing a mixture of olefin oligomers inaccordance with claim 4 wherein the aliphatic alcohol contains fromabout two to about 4 carbon atoms, the ketone contains from three toabout four carbon atoms and the polyol is ethylene glycol or propyleneglycol.
 6. A process for producing a mixture of olefin oligomers inaccordance with claim 1 wherein the partial pressure of the borontrifluoride is between about 20 and about 100 psig, the cocatalystmixture comprises between about 0.1 and about 1.0 weight percent of saidolefin, and the temperature is between about 20° C. and about 70° C. 7.A process for producing a mixture of olefin oligomers in accordance withclaim 1 wherein the olefin comprises 1-decene.
 8. A process forproducing a mixture of olefin oligomers in accordance with claim 4wherein the alcohol is n-butanol.